What do polar bears eat?
The polar bear's main prey is the ringed seal. Polar bears usually hunt ringed seals by waiting for the seals surface to breathe at openings (leads) in the ice or at breathing holes (aglus).
In fall, a seal cuts ten to fifteen aglus in the ice using the sharp claws on its foreflippers. It keeps the aglus open all winter long, even when ice is six feet (~2 meters) thick. Seals surface about every five to fifteen minutes at one of these breathing holes.
Polar bears locate breathing holes with their powerful sense of smell and lie in wait for the seals to rise. Polar bears have to be smart and patient because the wait can be long—from hours to days.
Seal stalking. Bears also stalk ringed seals that are basking on the ice by taking advantage of their sleep-wake rhythms. The bear crawls slowly forward and freezes in place when the animal raises its head. At about 20 feet from the seal, the bear pounces, killing the seal before it can escape back into the sea.
- Ringed seals are the most abundant seal in the circumpolar region north to the Pole. They live in water and on land-fast or solid ice, and sometimes on ice floes.
- Adult ringed seals have a thick layer of blubber and reach an average length and weight of 4.1 feet and 150 pounds. Their backs are dark and spotted with cream-colored rings. Underneath, their coats are white to creamy yellow.
- Seal pups are born in snow dens on land-fast ice in March and April. Their mother nurses them for about two months and pups learn to swim and hunt as the ice breaks up in early summer. The seal pupping season is a time of plenty for polar bears: naive young pups make easy prey.
Ice is a must. Polar bears depend on ice for access to their main prey.
- Polar bears' lives are a cycle of feasting and fasting. When hunting is good, polar bears eat only the seal's blubber and skin. They can eat 100 pounds of blubber in a single sitting! Younger, less experienced bears devour the remains, as do arctic foxes.
- Scientists have found that when polar bears dine exclusively on seal fat, their cholesterol levels drop lower than those of fasting bears because of the protective quality of the omega-3 fatty acids found in the seals.
- In summer, when ice floes retreat, some polar bears follow the ice—sometimes traveling hundreds of miles—to stay with their food source.
- Polar bears stranded on land in summer must stay put until the ice forms again in fall. On land, most bears face lean times. They rarely catch seals in open water.
Other foods. The polar bear is an opportunistic hunter, always alert to other food sources—including vegetation, geese, bird eggs, and even the occasional caribou, if available. Although some individual bears may benefit from eating these alternative foods, there is yet no evidence they could provide enough calories to sustain any of the existing populations of polar bears.
Polar bears also occasionally feed on other arctic marine mammals, including whales, walruses, and narwhals. Beluga whales or narwhals that become trapped in a savsatt—a small opening in pack ice—become easy prey for the bears. And whale carcasses on the shore offer a bonanza. None of these alternative marine foods are available on a predictable enough basis to offset the possible loss of ringed and bearded seals.
Bounty. Alaskan marine biologist Lloyd Lowrey observed a group of bears capture about 40 whales at a savsatt in the northern Bering Sea. And in 1999, 13 bears harvested beluga whales trapped in a savsatt near Canada's Ellesmere Island.
Dining etiquette. Russian scientist Nikita Ovsyanikov once observed about 100 polar bears around a gray whale carcass. He's also seen fourteen polar bears eating shoulder-to-shoulder at a single walrus carcass.
Though one bear may own a large carcass, he won't object to sharing if his guests beg properly. Begging involves a submissive, low-to-the-ground approach, followed by a slow circle around the carcass, and touching the nose of the bear in charge.